A number of different automated clinical chemical analyzers are known in the art. Such analyzers range from simple, largely manually-operated instruments to highly complex, nearly fully automated instruments. Each analyzer has its own particular performance characteristics related to the number of different tests ("menu") that the analyzer can perform and the number of samples that can be processed in a given period of time ("throughput").
Large scale, highly complex analyzers useful in large hospitals and clinical laboratories have been developed which have both a large menu of tests which the instrument can perform and a high throughput. Such an analyzer is described in U.S. Pat. No. 4,965,049 issued to Lillig et al. which is incorporated herein by reference in its entirety.
In U.S. Pat. No. 4,965,049, it is recognized that the throughput of a large menu analyzer can be increased by performing frequently requested analyses in high volume, limited menu analyzer modules separate from broader menu analyzer modules. Such high volume, limited menu modules are commonly used for such frequently requested analyses as sodium, potassium, glucose, creatinine and blood urea nitrogen ("BUN").
As sophisticated and efficient as many of today's large scale analyzers are, several problems continue to exist. First and foremost is throughput capacity. Every second which can be saved in the analysis time of each sample means millions of dollars in savings of precious medical resources. Therefore, there is continuous pressure on analyzer manufactures to increase throughput. In prior art high volume, limited menu modules, the required rinsing step between each analysis is carried out using the same reagent which is employed in the analysis. This results in a loss of module turnaround because the rinsing reagent must either be preheated (to maintain the temperature of the module) or (if non-preheated reagent is used) the module must be reheated after rinsing prior to its being used in another chemistry.
Also, in analyzing machines using nephelometry to analyze the results of the chemistry carried out within the module, throughput is reduced by having to periodically calibrate the nephelometer.
An additional problem is maintenance. Users of large scale analyzers require an extremely high standard of reliability. In high volume, limited menu analyzer modules which use nephelometry, several problems related to reliability exist in the prior art. Typically, the nephelometric analyzer uses a light source, a focusing lens, a receiving lens and a light receptor. In prior art nephelometric analyzer manufacturing processes, the forward end of the light source is, itself, shaped like a lens. However, the quality of such lens shaping varies from light source to light source. Thus, with every analyzer, the light energy emanating from the focusing "lens" varies depending upon the relative quality of alignment. In the prior art, the analyzing machine manufacturer had to compensate for these alignment problems by calibrating each analyzer after it was installed in the analyzing machine using modulating shutters disposed between the focusing "lens" and the reaction cup. Use of such shutters requires that the light source be operated at near maximum capacity. Thus, prior art light sources tend to burn out quickly. Also, a problem arises at the time that the light source burns out and needs to be replaced. The analyzer shutters have to be recalibrated anew. Since the recalibration operation is complex and requires considerable skill, the simple occurrence of a burned out light source bulb in the prior art causes a significant maintenance problem for the user.
Another problem with the prior art is reliability. In prior art light source modules, the light receptor housing is attached within the reaction cup using a bayonet connection. Minimum resistance to rotation in the bayonet connection is provided solely by the resilient pressing of the forward end of the receptor housing against a flexible O-ring. Unfortunately, this connection can easily be bumped out of alignment, such as by minor physical contact with the light receptor housing. Any such misalignment throws the analysis module out of calibration.
Still another problem with the prior art is that high volume, limited menu analyzer modules of the prior art are typically expensive to operate because they use a considerable amount of reagent (because the rinsing step mentioned above is carried out with expensive reagent) and because of excessive waste disposal costs (again, because potentially toxic reagent is often used as the rinsing agent).
Accordingly, there is a need for a high volume, limited menu analyzer module which has greater throughput than similar prior art analyzer modules, requires less maintenance, is more reliable and does not cost as much to operate.